The Collaborative International Dictionary of English v.0.48:

Chopper \Chop"per\, n.
   One who, or that which, chops.
   [1913 Webster]

WordNet (r) 3.0 (2006):

chopper
    n 1: a grounder that bounces high in the air [syn: chop,
         chopper]
    2: informal terms for a human `tooth' [syn: chopper, pearly]
    3: an aircraft without wings that obtains its lift from the
       rotation of overhead blades [syn: helicopter, chopper,
       whirlybird, eggbeater]
    4: a butcher's knife having a large square blade [syn:
       cleaver, meat cleaver, chopper]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "chopper":
   bicycle, bike, copter, cycle, eggbeater, helicopter, iron,
   minibike, motocycle, motorbike, motorcycle, pedicab, pig,
   road-bike, rotary-wing aircraft, rotor plane, trail bike, tricycle,
   trike, wheel, whirlybird, windmill